Reforming hydrocarbons for enhanced yields



Dec. 23, 1958 H. A. HOLCOMB ETIAL REFORMING HYDROCARBONS FOR ENHANCED YIELDS Filed Sept. 4, 1956 2 Smeets-SheetI l www JV om Dec. 23, 1958 yResearch Clear Octane No.

l05F and Heavier Product REFORMING HYDROCARBONS FOR ENHANCED YIELDS Filed Sept. 4, 1956 2 Sheets-Sheet 2 F IG. 2.

a0 a5 so 95 loo l05F and Heavier Yield, Val. Fresh Feed Example 0 l90260F Virgin Naphfha 3 20% Catalytic Penrylenes m Lasf-Reacrorm A 40% n 1| n n n 5 INVENTORS.

Robert M. Love, Henry A. Holcomb, YJames F. Mathis,

A United States Patent Office 2,865,837 Patented Dec. 23, 195s REFORMING HYDROCARBONS FOR ENHANCED YIELDS Henry A. Holcomb, Robert M. Love, and James F. Mathis, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, a corporation of Delaware Application September 4, 1956, Serial No. 607,639

11 Claims. (Cl. 208-65) The present invention is directed to a method for converting hydrocarbons. More particularly, the invention is directed to a method of producing high yields of high octane number hydrocarbons. In its more specific aspects, the invention is directed to converting naphthenic hydrocarbons in admixture with other hydrocarbons in high yields of high octane number materials,

The present invention kmay be briefly described as a method for producing enhanced yields of high octane number hydrocarbons in which a naphthenic hydrocarbon fraction is charged in series to a plurality of reaction Zones, each containing a bed of supported platinum catalyst and maintained at hydrocarbon conversion conditions. The specific feature of the present invention involves adding a normal paraflin in a sufficient amount to the naphthenic hydrocarbon feed at least to the lead reaction zone of said plurality of zones and adding an iso-olen in a suicient amount to the converted hydroi carbon charged to the tail reaction zone of the plurality of zones such that the normal parafn is co-ntacted with the catalyst for a time within the range from about 10 to about 20 seconds and such that the isooleiin is contacted with the catalyst for a time within the range of about 2 to about 5 seconds whereby enhanced yields of high octane number hydrocarbons are obtained. While it is preferred to add the normal paratln to the lead reaction zone, under sorne conditions, the normal paraffin may be added to the other of the plurality of zones depending en reaction conditions therein.

The naphthenic hydrocarbon fraction which may be employed as the feed may boil in the range from about 100 to about 400 F. and suitably may contain naphthenic hydrocarbons and paratlinic hydrocarbons and some aromatic hydrocarbons. It will be preferred, however, to maintain the amount of aromatic hydrocarbons at a minimum since these hydrocarbons do not undergo conversion in the reaction and since they already have high octane number values.

The normal parafn added to the lead reaction zone may suitably include normal paraffins having from 5 to 8 carbon atoms and may include normal pentane, normal hexane, normal heptane and normal octane.

The iso-olefin added to the tail reaction zone may suitably Vinclude either iso-mono-olefns or iso-diolefns such as isopentylenes, isohexylenes, .isoheptylenes and isooctylenes, 2-methyl-butadienel,3, and the like, such as the diolens corresponding 'to the iso-mono-olens given by way of example. Normal pentane and isopentylenes comprise preferred normal paraflins and iso- -mono-olens to be introduced into the operation. Suitable diolens may be obtained from the C6 fraction of catalytic naphthas such as catalytically cracked naphthas.

The amounts of normal .paran and the iso-monoolefin employed may range from vabout 10 to about 60 percent by volume of the naphthenic hydrocarbon feed.

The catalyst employed in the `present invention is a platinum catalyst and preferably is I'a supported platinum on alumina catalyst. The amount foffplatinum onthe catalyst is preferably about 0.6% by weight but amounts of platinum in the catalyst from about 0. 1% to 2.0% by weight may be employed. In some cases as much as 4.0% by weight may be used although the lesser range is preferred. The support is preferably highly purified aluminum oxide. The aluminum oxide may suitably be a gamma alumina or an eta alumina derived from con.- ventional sources of alumina hydrates or from specially derived alumina hydrates, such as those obtainable from aluminum alcoholates, phenolates, etc.

Temperatures employed in the practice of the present invention in the several reaction zones may range from about 800 to about 1000 F. The temperatures may progressively increase from the lead to the tail reaction zone within this range. The temperatures may increase incrementally from one reaction zone to another reaction zone from about 10 to about 100 F. However, the temperatures in the several zones may be approximately equal. Also, the temperatures in the lead zones may be greater than the 'temperature in the tail reaction zone.

Pressure employed in the practice of the present invention may range from about 200 to about 500 pounds per square inch gauge. A suitable and preferred pressure is about 300 pounds per square inch gauge.

The space velocity is preferably about 2.0 volumes of total feed hydrocarbon per volume of catalyst per hour entering the lead reaction zone. However, space velocities in the several zones may range from about 0.5 to about 5.0 v./v./hr., the space velocity in the tail zone increasing as hydrocarbon is added thereto.

The presence of hydrogen is required in the practice of the present invention and a preferred amount of hydrogen is about 4000 standard cubic feet of hydrogen yper barrel of to-tal feed. The amount of hydrogen may range from about 2000 to 6000 cubic feet per barrel of feed.

The reaction is preferably conducted in a plurality of reaction zones with the supported catalyst arranged in beds therein. However, it is to be understood that the operation may be conducted with a iluidized type `operatio-n wherein a fluidzed powdered catalyst of the nature described is suspended in the vaporized hydrocarbon. Addition of iso-olefins to fluidized systems should alleviate the diicult heat supply problem inherent therein.

The reaction may be conducted under adiabatic or isothermal conditions.

Of importance in the practice of the present invention is the contact time. Specifically, the normal parain should contact the catalyst in the several reaction zones for a time within the range from about l0 to about 20 seconds. The iso-mono-oleiin should contact the catalyst in the last or in several reaction zones for -a time within the range from about 2 to about 5 seco-nds. By employing such contact times, the normal paran is isomerized selectively to isoparan and the iso-mono-olen is hydrogenated selectively to the corresponding isoe parain. Such reactions result in the enhancement of the quantity of isoparains in the product and result in a product which has an increased yield of isoparaflns as well as containing increased yields of aromatics pro.- duced from the reforming of the naphthenic hydrocarbons.

It is to be emphasized that the nephthenic hydrocarbon fraction which normally contains parains will have some of the parafiins isomerized to isoparains.

The present invention will 'be further illustrated 'by reference to the drawing in which:

Fig. l is in the form of a diagrammatic ow sheet of a preferred mode; and

Fig. 2 is a graph of data showing the relationship between the research clear octane number and the yield obtainable in the several examples.

Referring specifically to Athe drawing, numeral 11 vdesignates a charge line by way of which a naphthenic hydrocarbon fraction boiling in the range indicated is introduced into the system from a source not shown. The naphthenic hydrocarbon fraction is introduced into a heater or furnace 12 provided with heating coils 13 and supplied with heat through gas burners 14 which raise ,the temperature of the naphthenic hydrocarbon to the desired range. The heated and vaporized hydrocarbon then passes from the furnace 12 by way of line 15; normal paraffin, such as normal pentane, is injected thereto .by Way of line 16 controlled by line 17 and hydrogen is added thereto by way of line 18 controlled by valve 19 or recycled hydrogen is introduced into line 18 by recycle line 20 controlled by valve 21 from a source to be described hereinafter. In any event. the mixture of naphthenic hydrocarbon, normal paraiilin and hydrogen, the latter preferably being heated either separately or with the naphthenic hydrocarbon, is introduced by way of line 22 into a lead reaction zone 23 which contains a bed 24 of platinum catalyst, of the nature specilied before, arranged on a grid plate 25. The hydrocarbon feed mixtureis converted in reaction zone 23 and the converted or partially converted hydrocarbons issue therefrom by way of line 26 controlled by valve 26a which discharges the partially converted product including the normal parain into a heater or furnace 27 provided with a heating coil 28 and heated by means of gas burners 29. The reheated and partially converted product is then routed by way of line 30 into a second reaction zone 31 provided with a bed of platinum catalyst 32 arranged on a grid plate 33. It may be desirable to bypass all or part of the partially converted products from reaction zone 23 around the heater 27 and to this end bypass line 34a controlled by valve 35a is provided.

The partially converted products discharge through the bed 32 of reaction zone 31 and are further converted with the converted products discharging therefrom through line 34 controlled by valve 35 into a heater or furnace 36 provided with heating coils 37 and gas burners 38. The reheated products then discharge from furnace 36 by way of line 39 into reaction zone 40 which is provided with a bed of platinum catalyst 41 supported on grid plate 42. Bypass line 43a controlled by valve 44a is also provided to allow the converted products from zone 31 to bypass the furnace 36 in part or completely as may be desired.

The products are further converted in reaction zone and are discharged therefrom by way of line 43 controlled by valve 44 into a heater or furnace 45 provided with a heating coil 46 and heated with gas burners 47. The converted products are discharged from furnace into line 48 and then introduced thereby into a tail reaction zone 49 in admixture with an isoolefin introduced by line 48a controlled by valve 48h. Zone 49 is provided with a bed 50 of supported platinum catalyst on grid plate 51. It is understood that the iso-olefin may be added to line 43 and heated in furnace 45 or may be separately heated.

The converted products issue from zone 49 by way of line 52 and are discharged thereby into a separation zone 53. It may be desirable to bypass the furnace 45 and to this end bypass line 53a is provided controlled by valve 54a allowing the furnace 45 to be completely or partially Ibypassed by the converted products.

The converted products are discharged by line 52 into separation zone 53 by way of which a separation is made between the normally gaseous constituents and the normally liquid constituents7 the gases being discharged by line 54, compressed, as required, and recycled by way of line 20 to line 18. If the amount of fixed gases which include hydrogen exceed the amount required in the several reaction zones, then the hydrogen-containing gases may be discharged by opening valve 5S in line 21.

The liquid product is withdrawn from separation zone 53 by line 56l and discharged thereby into a fractional distillation zone 57 which may be a singleA fractional distillation tower or a plurality of fractional distillation towers. For purposes of briefness, zone 57 is shown as a single fractional distillation tower which it will be understood to include internal Vapor-liquid contacting means, such as bell cap trays, and the like, auxiliary equipment, such as reiluxing, cooling and condensing equipment, and the like.

ln the drawing, zone 57 is provided with a heatlng means illustrated by a steam coil 58 and is provided with lines 59, 60, 61, and 62 for withdrawal of desirable products therefrom. A bottoms fraction may be withdrawn by line 63. The fractions withdrawn by lines 59, 60, 61 and 62 may include converted isoparatiins, and aromatics or mixtures thereof. The bottoms fraction in line 63 and the side stream fraction of line 62 may include unconverted hydrocarbons and may be recycled to line 11 as desired.

By operating in accordance with the present invention, a suitable reaction or contact time is provided for the normal parafiins and a suitable reaction time is provided for the iso-mono-oletns, such that enhanced yields of the aromatic and isoparanic hydrocarbons are obtained.

The invention will be further illustrated by the following examples:

EXAMPLE l Table I Research Clean 105 F. and Heavlcr Product Yleld, Vol. Percent Octane Number on Fresh Feed of 105 F. and

Hcavier Product.

It was found that at 85 Research clear octane number the contact time was about 16.8 seconds. The inlet temperatures to the several reactors varied from about 900 to about 975 F.

EXAMPLE 2 A blend of 20 volumes of a pentylene-rich stream ob tained from a catalytic cracking operation and volumes of a 260 to 300 F. virgin crude naphtha was reformed under the same conditions as Example 1 with reaction inlet temperatures of 945, 956, 954 and 955 in the four reactors, respectively.

The catalyst temperatures in the four reactors were 908, 934, 941, and 952, respectively. The yield of iso and normal pentanes based on the components of the pentylene feed was 66.4 mol percent. The ratio of isopentane to normal pentane in the product was 1.83 cornpared to 1.94 which would have been obtained if only hydrogenation of the pentylenes been effected. The contact time was about 16.8 seconds.

It may be concluded from these results that the hydrogenation of pentylenes for the conversion of isopentylene to isopentane may be effectively carried out only by operating at lower contact times than those in this` example.

EXAMPLE 3 The same crude virgin naphtha of Example 1 was reformed under the same conditions of Example 1 with reactor inlet temperatures of 924, 935, 934 and 934, respectively, in the four reactors in series. The average catalyst bed temperatures corresponding to these inlet temperatures were 830, 867, 879, and 896 F., respectively. The yield octane relationship obtained in the product from this run was as follows:

105 F. and heavier product yield, vol. percent on feed 86.2 105 F. and heavier product, Research clear octane number 85 EXAMPLE 4 Immediately following Example 3 with the same reactor inlet temperatures on the same virgin crude naphtha, catalytic pentylenes, the analysis of which follows, were charged to the inlet of the fourth or last reactor at a rate of 20 volume percent of the total virgin crude naphtha feed to the lead reactor. The hydrogen recycle gas rate was increased so that a rate of 4,000 standard cubic feed of hydrogen per barrelof total feed to the reactor system was maintained. The reactor inlet temperatures were 926, 937, 933 and 931 F. prevailing for the several reactors in series at corresponding average catalyst bed temperatures of 835, 872, 881 and 939 F. The increase in the average temperature in the last reactor was occasioned by the exothermic nature of the hydrogenation reactions involving the pentylenes, it being understood that the reactions in reforming are normally endothermic in nature and require reheating between reactors.

Table l-Catalytic pentylenes analysis Compound: Wt. percent i-Pentane 30.2 n-Pentane 2.8 Pentene-l 10.3 Trans-pentene-2 11.4 Cispentene-Z 9.5 2 M-butene-l 12.0 2 Mbutene2 20.6 105 F. and heavier 3.2

The 105 E. plus product yield based on the virgin crude naphtha charged in this example was 85.6 volume percent with a research clear octane number of 89.3. This represents a yield advantage of about 1.9 volume percent at the 89.3 octane level over that shown in Example 1 for operations with the same virgin crude naphtha alone. The higher octane number level in this example over Example 3 at the same inlet reactor temperatures was obtainable by the higher average reactor temperature in the fourth or tail reactor. ln Example 4 herein the overall contact time was 14.1 seconds whereas the contact time in the last reactor was 3.3 seconds.

ln addition to the increase in the 105 F. plus product from the virgin naphtha the yield of iso plus normal pentane from the pentylenes added to the last reactor was 81.1 mol percent of that which would have been obtained by hydrogenation alone. The mol ratio of isopentane to normal pentane in the product from pentylenes was 1.94 compared to 1.83 for the pentylenes introduced into the last reactor zone. This showed that isopentane would not isomerize to normal pentane after it has been formed by hydrogenation.

6 EXAMPLE 5 The conditions of Example 4 were maintained and an additional 20 volume percent, making a total of 40`volurne percent of a catalytic pentylenes based on the total virgin naphtha feed, were added to the last reaction zone feed. Reactor inlet temperatures of 924, 934, r936 and 866 provided averagerreactor or catalyst tempera'- tures of 834, 871, 887 and y940 F. in this example. Again the recycle gas rate was increased to maintain a rate of 4,000 standard cubic feet of hydrogen per barrel of total feed to the reactor system. Under these conditions, the yield of 105 F. and heavier materials based on the virgin crude naphtha was 86.4 volume percent for a research clear octane number of 88.1. This represents a yield advantage of about 1.9 volume percent at the 88.1 octane level over that shown for Example 1 for operations with the virgin crude naphtha alone. In this run the total contact time was 12.4 seconds and the contact time in the fourth reactor was only about 2.8 seconds. The yield of iso plus normal pentanes was 92.4 mol percent of that which would have been made by hydrogenation alone with no loss. The mol ratio of iso to normal pentane in the pentylenes product was 1.93 compared to 1.83 for the pentylenes feed. The yield of isopentane was 94.1 mol percent of that. available from the pentylene feed. The similar yield for normal pentane was 89.3 mol percent. This example conclusively shows that the yield-product distribution relationships were better from the standpoint of pentylenes alone at 40 volume percent level in the last reactor than at the 20 volume percent level.

EXAMPLE 6 Example No. 4 was repeated except that 20 volume percent of the crude virgin naphtha of a normal pentanerich fraction were added to the fourth reactor instead of the catalytic pentylenes. With reactor inlet temperatures of 923, 934, 934 and 933 the average reactor temperatures were 831, 870, 882, and 903 F. The

In this operation the contact time in the fourth .reactor was about 3.4 seconds.

Under the conditions of this example the yields of 105 F. and heavier material produced from the virgin crude naphtha was 88.7 volume percent and the octane number was 84.3 research. This represents a yield advantage of 1.7 volume percent of 105 F. and heavier fraction'at 84.3 research octane number over .that obtained with the virgin crude naphtha alone with the same octane number. The yield of iso plus normal pentanes was mol percent of that from the feed pentanes. The mol ratio of iso to normal pentane was 0.39 compared to 0.26 for the feed. The isopentane yield based on feed isopentane was 139.2 mol percent indicating that some isomerization of normal pentane to isopentane occurred.

The data in these several examples are presented in Fig. 2 graphically and show conclusively an improved yield for the presence of catalytic pentylenes in the last reaction zone.

From these examples it is clear that it was desirable to add the normal paraflns to the lead reaction zone of a plurality of reaction zones to enhance the isomerization thereof by providing the extended contact time whereas it is desirable to add the iso-mono-olen to the tail reaction zone such that the iso-mono-olen is only hydrogenated but is not further converted.

The present invention is of great value and utility in ythat enhanced yields of high octane number material are 7 Y possible by operating the reforming zone employing a platinum catalyst in which the parain is subjected to a relatively long reaction time and the iso-mono-olelin is subjected to a relatively short reaction time.

It is contemplated that the present invention may be operated by providing an elongated reaction zone containing a bed of supported platinum catalyst maintained at hydrocarbon conversion conditions such as described herein with the parainic hydrocarbon being charged to the feed to said reaction zone and with the iso-monoolefin being charged into the reaction zone at a selected intermediate point therein to provide the relatively long contact time for the normal paraffin and the relatively short contact time for the isoparaiin.

The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and to secure by Letters Patent is:

1. A method for producing enhanced yields of high octane hydrocarbons in which a naphthenic hydrocarbon fraction is charged in series to a plurality of reaction zones each containing a bed of supported platinum catalyst and maintained at hydrocarbon conversion conditions which comprises adding a normal parain in a sufficient amount within the range from about 10 to about 60% by Volume of the naphthenic hydrocarbon to the naphthenic hydrocarbon feed to the lead reaction zone oi said plurality of zones and adding an isoolen in a sutlicient amount within the range from about l to about 60% by volume of the naphthenic hydrocarbon to the converted hydrocarbon charged to the tail reaction zone of said plurality of zones such that the normal paran is contacted with the catalyst for a time Within the range from about to about 20 seconds and such that the isoolen is contacted with the catalyst for a time within the range from about 2 to about 5 seconds whereby enhanced yields of high octane hydrocarbons are obtained.

2. A method in accordance with claim 1 in which the normal parafn is normal pentane and the iso-olen is an isopentylene.

3. A method in accordance with claim 1 in which the plurality of reaction zones comprise four reaction zones maintained at conversion conditions including a progressively increasing temperature from the lead to the tail reaction zone within the range from about 800 F. to about 1000" F.

4. A method in accordance with claim 1 in which the iso-olefin is an iso-mono-olefin.

5. A method in accordance with claim 1 in which the iso-olefin is an iso-diolen.

6. A method for producing enhanced yields of high octane hydrocarbons in which a naphthenic hydrocarbon fraction boiling in the range from about 100 to about 400 F. is contacted in the presence of a free hydrogencontaining gas in series with a platinum catalyst in a plurality of reaction zones each containing a bed of supported catalyst containing from about 0.1% to about 4.0% by weight of platinum on purified alumina and maintained at hydrocarbon conversion conditions which comprises adding a normal parain containing 5 to 8 carbon atoms in a sufcient amount within the range from about l0 to about 60% by volume of the naphthenic hydrocarbon to the naphthenic hydrocarbon feed to the lead reaction zone of said plurality of zones and adding an isomono-olen containing 5 to S carbon atoms in a sufficient amount within the range from about 10 to about 60% by volume of the naphthenic hydrocarbon to the converted hydrocarbon charged to the tail reaction zone of said plurality of Zones such that the normal parain is contacted with the catalyst for a time within the range from about 10 to about 20 seconds and such that the iso-mono-olen is contacted with the catalyst for a time Within the range from about 2 to about 5 seconds whereby enhanced yields of high octane hydrocarbons are obtained.

7. A method in accordance with claim 6 in which the normal parafn is normal pentane and the iso-mono-oletn is an isopentylene.

8. A method in accordance with claim 6 in which the plurality of reaction zones comprise four reaction zones maintained at conversion conditions including a progressively increasing temperature from the lead to the tail reaction zone within the range from about 800 F. to about 1000 F.

9. A method in accordance with claim 6 in which the conversion conditions in saidplurality of reaction zones includes a temperature increasing incrementally from one reaction zone to another by about 10 F. to about 100 F.

l0. A method in accordance with claim 6 in which the conversion conditions include a pressure within the range from about 200 to about 500 pounds per square inch gauge and a space velocity in the range from about 0.5 to about 5.0 volumes of hydrocarbon fraction per volume of catalyst per hour.

1l. A method for producing enhanced yields of high octane hydrocarbons in which a naphthenic hydrocarbon fraction is charged to a reaction zone containing a bed of supported platinum catalyst and maintained at hydrocarbon conversion conditions which comprises adding a normal parain in a sucent amount within the range from about 10 to about 60% by volume of the naphthenic hydrocarbon to the naphthenic hydrocarbon feed and adding an iso-olefin to said reaction zone in a suicient amount within the range from about 10 to about 60% by volume of the naphthenic hydrocarbon at a selected point such that the normal paraffin is contacted with the catalyst for a time within the range from about 10 to about 20 seconds and such that the iso-olefin is contacted with the catalyst for a time within the range from about 2 to about 5 seconds whereby enhanced yields of high octane hydrocarbons are obtained.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD FOR PRODUCING ENHANCED YIELDS OF HIGH OCTANE HYDROGEN IN WHICH A NAPHTHENIC HYDROCARBON FRACTION IS CHARGED IN SERIES TO A PLURALITY OF REACTION ZONES EACH CONTAUNUNG A BED OF SUPPORTED PLATINUM CATALYST AND MAINTAINED AT HYDROGEN C/NVERSION CONDITIONS WHICH COMPRISES ADDIING A NORMALPARAFFIN IN A SUFFICIENT AMOUNT WITHIN THE RANGE FROM ABOUT 10 TO ABOUT 60, BY VOLUME OF THE NAPHTHENIC HYDROCARBON TO THE NAPHTHENIC HYDROCARBON FEED TO THE LEAD REACTION ZONE OF SAID PLURALITY OF ZONES AND ADDING AN ISOOLEFIN IN A SUFFICIENT AMOUNT WITHIN THE RANGE FROM ABOUT 10 TO ABOUT 60% BY VOLUME OF THE NAPHTHENIC HYDROCARBON TO THE CONVERTED HYDROCARBON CHARGED TO THE RAIL REACTION ZONE OF SAID PLURALITY OF ZONES SUCH THAT THE NORMAL PARAFFIN IS CONTACTED WITH THE CATALYST FOR A TIME WITHIN THE RANGE FROM ABOUT 10 TO ABOUT 20 SECONDS AND SUCH THAT THE ISOOLEFIN IS CONTACTED WITH THE CATALYST FOR A TIME WITHIN THE RANGE FROM ABOUT 2 TO ABOUT 5 SECONDS WHEREBY ENHANCED YIELDS OF HIGH OCTANE HYDROCARBONS ARE OBTAINED. 